1. Field of the Invention
This invention generally relates to an electrophotographic photoreceptor and an image forming device that employs the same, such as laser printers, electrostatic copying machines, plain paper facsimile devices, and multi-function devices which combine all of these functions.
2. Background Information
A conventional image forming device electrostatically charges the surface of an electrophotographic photoreceptor, exposes an original document having an image thereon, and forms an electrostatic latent image on the electrophotographic photoreceptor that corresponds to the image on the original document. After developing the electrostatic latent image with toner, the image forming device transfers the toner formed on the electrophotographic photoreceptor to a recording medium such as paper. The recording medium is then separated from the electrophotographic photoreceptor, the toner thereon is fixed, and an image is formed thereon. After the toner is transferred to the recording medium, any remaining toner left on the surface of the electrophotographic photoreceptor is removed by a cleaning step as needed. The electrostatic charge is then removed from the surface of the electrophotographic photoreceptor, and the electrophotographic photoreceptor is then supplied with another electrostatic charge in order to form an image on another recording medium.
The photoreceptor is composed of a resin layer (e.g., a photosensitive layer and an intermediate layer) that is formed on the surface of an electroconductive substrate. The resin layer is formed on the surface of the electroconductive substrate by applying a liquid resin thereon that is obtained by dissolving a binding resin in an organic solvent. A metal tube composed of aluminum or an aluminum alloy is generally used for the electroconductive substrate, which has excellent heat resistance and is comparatively lightweight.
However, when the resin layer is applied to the surface of an aluminum or aluminum alloy substrate, the thickness of the resin layer will be irregular because the adhesiveness of the liquid resin to the substrate is low, and therefore an irregular image will be transferred to a recording medium. In addition, although this type of substrate is lighter than other metal substrates, large size substrates will be correspondingly heavy, and thus a large amount of torque will be required to drive them.
Furthermore, when the aforementioned materials are used as is in the aforementioned conventional substrate, a charge that is higher than necessary will be placed on the resin layer because these materials have an extremely high conductivity. Thus, the surface potential of the photoreceptor will decline, and a foggy and low density image will be produced. In order to prevent this defect from occurring, others have previously proposed forming an alumite layer on the surface of the substrate. However, this increases the cost of the electrophotographic photoreceptor.
In addition, a method of preventing a charge that is greater than necessary from being placed on the resin layer has been proposed in which the alumite layer is replaced with an intermediate layer that is primarily composed of a resin and formed on the surface of the substrate. By including a pigment in the intermediate layer, the light used during exposure will normally be absorbed by the pigment and not be reflected by the surface of the substrate, and thus preventing interference fringes. However, the materials that can be used as a pigment are limited to metal oxides with low conductivity such as titanium oxide and the like because of the need to preserve a certain degree of insulation in the intermediate layer.
In view of the above, there is a need for a substrate for an electrophotographic photoreceptor which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.